Study On Consolidation Of Granular Column/sand Well Foundation By Vacuum-heap Preloading

In this paper,the consolidation solution of foundation under vacuum-surcharge preloading and sand well foundation group consolidation solution under vacuum preloading and vacuum-surcharge preloading are studied.The main work are as follows:(1)Study on the problem of radial consolidation of the composite foundation of vacuum-surcharge preloading granular column composite foundation,a spatial axisymmetric deformation calculation model is established.Displacement method is used to calculate the deformation and volume strain of the soil,and then the analytical solution of radial consolidation of the composite foundation of vacuum-surcharge preloading considering the vacuum attenuation and well resistance is derived.The correctness of the analytical solution is verified by comparing the degradation analysis and special case analysis with the existing solution.Furthermore,the influence of various parameters on consolidation rate of composite foundation is plotted through calculation of an example.The results show that the smaller the pile diameter ratio,slenderness ratio and influence factors in disturbed areas are,the faster the consolidation rate of composite foundation is.The greater the radial time factor,the higher the radial consolidation degree of composite foundation.(2)In view of the consolidation problem of vacuum-surcharge preloading composite foundation considering the load application process and the change of soil radial permeability coefficient in drainage affected zone,a calculation model is established,and the consolidation equation of vacuum-surcharge preloading composite foundation considering variable load is given by using equilibrium conditions and basic assumptions,and its general solution is obtained by using the separation variable method.The correctness of this solution is verified by degradation analysis and comparison with existing solutions.Furthermore,the calculation expressions of average pore pressure and average consolidation degree under single-stage constant velocity loading are obtained.Through calculation of examples,the graph of the influence of various parameters on consolidation rate of composite foundation is drawn.Studying the curves in each figure shows that the higher the pile-soil compression modulus ratio,the smaller the pile diameter ratio,and the smaller the disturbance area size factor,the faster the consolidation rate of composite foundation.(3)Aiming at the consolidation problem of vacuum preloading sand well foundation group wells,considering the influence of vacuum degree attenuation,the radial consolidation solution of vacuum preloading sand well foundation group wells is deduced,and the rationality of the solution is verified through degradation analysis research.Through calculation of some examples,the graph of the influence of various parameters on consolidation of sand well foundation group wells is drawn.The curve law in the research map shows that the smaller the ratio of group well unit radius to sand well radius and the more side wells,the faster the consolidation of foundation.(4)Establish a consolidation calculation model of vacuum-surcharge preloading sand well foundation group wells considering vacuum degree attenuation and well resistance.By using analytical solution,the radial consolidation solution of vacuum-surcharge preloading sand well foundation group wells is given,and the correctness of this solution is verified through degradation analysis research.Through calculation of some examples,the graph of influence of various parameters on consolidation of sand well foundation group wells is drawn.By studying the curves in each figure,it can be obtained that during the consolidation process,the greater the vacuum load and pile load,the more the number of side wells,the faster the consolidation.